The present invention relates to apparatus and methods for filtering or removing matter from within a vascular system. More particularly, the present invention provides a low profile self-expanding vascular device useful for capturing emboli generated during interventional procedures, and for thrombectomy and embolectomy.
Percutaneous interventional procedures to treat occlusive vascular disease, such as angioplasty, atherectomy and stenting, often dislodge material from the vessel walls. This dislodged material, known as emboli, enters the bloodstream, and may be large enough to occlude smaller downstream vessels, potentially blocking blood flow to tissue. The resulting ischemia poses a serious threat to the health or life of a patient if the blockage occurs in critical tissue, such as the heart, lungs, or brain.
The deployment of stents and stent-grafts to treat vascular disease, such as aneurysms, also involves the introduction of foreign objects into the bloodstream, and also may result in the formation of clots or release of emboli. Such particulate matter, if released into the bloodstream, also may cause infarction or stroke.
Numerous previously known methods and apparatus have been proposed to reduce the risk of embolism. Zadno-Azizi et al. U.S. Pat. No. 5,833,644, for example, describes the use of balloon-tipped catheter to temporarily occlude flow through a vessel from which a stenosis is to be removed. Stenotic material removed during a treatment procedure are evacuated from the vessel before the flow of blood is restored. A drawback of such previously known systems, however, is that occlusion of antegrade flow through the vessel may result in damage to the tissue normally fed by the blocked vessel.
U.S. Pat. No. 5,814,064 to Daniel et al. describes an emboli filter system having a radially expandable mesh filter disposed on the distal end of a guide wire. The filter is deployed distal to a region of stenosis, and any interventional devices, such as an angioplasty balloon or stent delivery system are advanced along the guide wire. The filter is designed to capture emboli generated during treatment of the stenosis while permitting blood to flow through the filter. Similar filter systems are described in Wholey et al. U.S. Pat. No. 4,723,549 and Cassell et al. U.S. Pat. No. 5,827,324.
One disadvantage of radially expandable filter systems such as described in the foregoing patents is the relative complexity of the devices, which typically comprise numerous parts. Connecting more than a minimal number of such parts to a guide wire generally reduces the ability of the guide wire to negotiate tortuous anatomy, and increases the profile of the device in its delivery configuration. Consequently, it may be difficult or impossible to use such devices in small diameter vessels such as are commonly found in the carotid artery and cerebral vasculature. Moreover, such filter devices are generally incapable of preventing material from escaping from the filter during the process of collapsing the filter for removal.
International Publication No. WO 98/39053 describes a filter system comprising an elongated member, a radially expandable hoop and a cone-shaped basket. The hoop is affixed to the elongated member, and the cone-shaped basket is attached to the hoop and the elongated member so that the hoop forms the mouth of the basket. The filter system includes a specially configured delivery catheter that retains the mouth of the basket in a radially retracted position during delivery.
While the filter system described in the foregoing International Publication reduces the number of components used to deploy the cone-shaped basket, compared to the radial strut-type filter elements described hereinabove, it too has drawbacks. Chief among these, it is expected that it will be difficult to reduce the diameter of the radially expandable hoop to its retracted position. In particular, as the hoop is contracted through smaller radii of curvature, the stiffness of the hoop is expected to increase dramatically. This increased stiffness prevents the hoop from being contracted more tightly, and is expected to result in a delivery profile too large to permit use of the device in critical regions of the body, such as the smaller coronary arteries, carotid arteries, and cerebral vasculature.
In view of the foregoing disadvantages of previously known apparatus and methods, it would be desirable to provide a vascular device, e.g., for use as a vascular filter that, overcomes such disadvantages, and employs few components.
It also would be desirable to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels.
It further would be desirable to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters.
It still further would be desirable to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
In view of the foregoing, it is an object of the present invention to provide a vascular device that overcomes disadvantages of previously known vascular filters and thrombectomy/embolectomy devices, and employs few components.
It also is an object of this invention to provide a vascular device that is capable of being contracted to a small delivery profile, thus permitting use of the device in small vessels.
It is a further object of the present invention to provide a vascular device that is capable of being contracted to a sufficiently small profile that it may be retrieved using the guide wire lumen of previously known treatment devices, and without the need for specialized delivery catheters.
It is another object of this invention to provide a vascular device that reduces the risk of emboli or thrombus removed from the vessel wall escaping from the device when the device is collapsed and removed.
These and other objects of the present invention are accomplished by providing a vascular device, suitable for use as a vascular filter or thrombectomy/embolectomy device that comprises a blood permeable sac affixed at its perimeter to a support hoop having an articulation region. The support hoop is attached in a distal region of an elongated member, such as a guide wire, and supports a proximally-oriented mouth of the sac when the device is deployed in a vessel. In accordance with the principles of the present invention, the support hoop includes a reduced-thickness articulation region, generally opposite the point of attachment of the support hoop to the guide wire, that enables the support hoop to be contracted to very small radii of curvature without the problems of increased stiffness and kinking of previously known devices. In alternative embodiments, several hoops may be used in conjunction to facilitate opening and closing of the sac.
The support hoop preferably also has a curved profile, so that the articulation region is oriented in a direction approximately parallel to a vessel wall when the vascular device is deployed. This prevents the articulation region, when folded, from damaging the wall of the vessel, and permits the device to effectively contact the walls of the vessel and reduce emboli or thrombus removed from the vessel wall from bypassing the sac. Moreover, the articulation region when combined with a support hoop having a curved profile, causes the sides of the support hoop to fold inwards towards one-another when the vascular device is collapsed into a sheath for removal. This in turn closes the mouth of the sac and reduces the potential for emboli or thrombus to be released from the vascular device during removal.
Advantageously, use of an articulation region permits the vascular device of the present invention to be contracted to very small diameters, thereby enabling the use of delivery catheters having diameters less than 3 Fr. Moreover, the vascular device of the present invention may be retracted within the guide wire lumen of conventional treatment devices, such as angioplasty catheters and stent delivery systems, thereby obviating the need to re-insert a specialized delivery catheter to remove the vascular device.
In embodiments of the system of the present invention suitable for use as embolic filters, the vascular device may include a separate guide wire for introducing treatment devices proximal to the deployed vascular device, and the support hoop may form one or more additional loops or turns when deployed in a vessel to enhance the stability of the filter within the vessel. In yet other embodiments, a delivery sheath is provided that permits a lesion to first be crossed with an unencumbered guide wire, prior to passing the vascular device across the lesion. Methods of using the vascular device of the present invention are also provided, including, in the context of a vascular filter, the use of a previously known balloon catheter to arrest antegrade flow through a vessel until the vascular device of the present invention is deployed.